I'm using an Intel D945GNT mother board with a P4 3.2GHz Prescott on my rack computer. Works good with my Motu PCI.
You'd probably want something with a fast bus (look for FSB in the spec) speed and SATA controllers and find a processor that will fit into that. Or vice versa.
Can anyone show me a specific board they've had good luck with or would suggest that would go with an Athlon? Also, is PCIe or whatever alot better? I mgiht just change over to firewire. i dont know.